An MR head for high density recording has been used widely in hard disk applications. An MR head has recently come to be applied to backup tape systems. The MR head used in a backup tape system has its MR element recessed several tens of nanometers so as to avoid direct contact with tape and to prevent resultant wear. Causing a spacing loss, nevertheless, the recession should be minimized to realize high density recording. It is a technical difficulty to solve both the wear and spacing loss problems.
A dual-layer magnetic recording medium having a non-magnetic lower layer and a thin magnetic upper layer has been proposed as a medium suitable for high density recording. It has also been proposed to provide a thin magnetic upper layer with specific projections in order to satisfy both running durability and electromagnetic characteristics. For instance, JP-A-9-115130 proposes a magnetic recording medium that exhibits improved running durability while retaining excellent electromagnetic characteristics. The proposed medium has a magnetic layer with a thickness of 0.05 to 0.9 μm on a non-magnetic layer, the magnetic layer having specific densities of projections of specific heights as measured by atomic force microscopy (AFM). However, the height of the projections specified in claim 1 of JP-A-9-115130 (i.e., 25 to 40 nm) is greater than the depth of the recess of the MR head, and therefore the magnetic recording medium abrades the MR element easily.
With respect to the MR head wear problem, JP-A-2001-325709 discloses a magnetic recording medium having a specific density of 5 to 10 nm high projections of abrasive grains. JP-A-9-128739 teaches that MR head wear can be reduced by lowering the height of projections of abrasive grains than that of projections of particles other than abrasive grains so as to avert direct contact of the head with the abrasive grains.
The medium of JP-A-2001-325709 produces insufficient cleaning effects because of lack of height of abrasive projections and easily causes head contamination. The medium of JP-A-9-128739 is effective when combined with an 8 mm video head as described but insufficient for an MR element having a soft film.